Many human and animal diseases, including cancer, are associated with changes in cellular immunity (delayed hypersensitivity) and in production of lymphokines (non-antibody mediators of cellular immunity). It has been difficult in the past to quantitate these changes accurately in vitro, a difficulty which might be overcome if there were an antibody available which was specific for a lymphokine associated with cellular immunity; this antibody could be used to develop a radioimmunoasay to measure cellular immunity in vitro to tumor and other antigens. Macrophage agglutination factor (MAggF) is a lumphokine derived from antigen stimulated guinea pig lymph node cells with cellular immunity to antigen; similar activities have been reported in appropriately stimulated culture supernates of human and animal mononuclear cells. The chemical and physical nature of this lymphokine are poorly understood and its exact role in cellular immune reactions in vivo remains undefined. The proposed project will attempt to isolate guinea pig MAggF from concentrated culture supernates of antigen-stimulated guinea pig lymph node cells by sequential fractionation of these supernates by affinity chromatograph over insolubilized gelatin, preparative isoelectric focusing and gel filtration chromatography. Isolated and purified active MAggF will be characterized and used to raise antisera in rabbits. The specificity of these antisera for MAggF will be determined. The characterized antisera will be then used to evaluate the role of MAggF in vivo cellular immunity and to quantitate in vitro models of these reactions.